We propose to study the proximal convoluted tubules in Heymann nephritis, also called autologous immune complex nephritis (AICN), a model for human membranous glomerulonephritis. Antigens of tubular brush border (BB) and BB antibodies appear to be important in the immunopathogenesis of glomerular immune deposits in AICN. We wish to evaluate the possible role of BB autoantibodies in causing damage to proximal tubules in AICN. The morphology of tubules in rats with AICN will be studied by light and electron microscopy. Immune deposits will be examined by immunofluorescence and immunoelectronmicroscopy. Immunoelectronmicroscopy will be used to determine the distribution of BB antigen in normal tubules and its fate in AICN. By similar techniques, the deposition of IgG within tubules will be studied during the course of AICN. Those observations will be correlated with antibody titers and urinary protein composition to define discrete stages of tubular damage and recovery. Renal physiology in AICN will be studied to characterize functional impairment which may be associated with immunopathology. Rats with BSA immune complex glomerulonephritis will be studied for comparison and controls. The cytotoxicity of BB antibody will be tested in passive transfer experiments. Rat anti-BB IgG will be injected intravenously into rats with increased glomerular permeability caused by CSS glomerulonephritis. Under these conditions, IgG is quickly deposited along BB in vivo. Changes in morphology and function which follow deposition of rat anti-BB IgG in normal tubules will be studied at short intervals after the passive transfer. Microinjection of anti-BB IgG directly into normal tubules will also allow measurement of the effect of interaction of BB antibody with specific antigen.